This measure is published by Public Health England. It is based on a survey. The number is the percentage of respondents scoring 0-4 to the questions "Overall, how satisfied are you with your life nowadays".
Responses are given on a scale of 0-10 (where 0 is “not at all satisfied” and 10 is “completely satisfied”). The data shows the percentage of those scoring 0-4 (respondents in that area that scored themselves the lowest marks) in the question: 'Overall, how satisfied are you with your life nowadays?' .The smaller the percentage of residents not satisfied with their life, the happier residents are over all.
The raw data is available to view or download from Herefordshire's Data Hub